Widespread pustular eruption following probiotic use.

A 26-year-old woman with Crohn disease and palmoplantar psoriasis on ustekinumab presented with a diffuse and intensely pruritic rash with a few pin-point pustules within days after initiation of an over-the-counter Align brand probiotic. Biopsy revealed psoriasiform and spongiotic dermatitis with spongiform subcorneal pustules and scattered eosinophils, consistent with acute generalized exanthematous pustulosis. Our case highlights a unique presentation of acute generalized exanthematous pustulosis following probiotic exposure with fewer than usual pustular lesions. IL23 suppression by ustekinumab may have contributed to the patient's reduced pustular presentation.